More than one friend has asked the author about this topic. Today, the author will explain why, but the title is not strict enough in the strict sense, but in order to let everyone understand the author at once, the title is set up like this. What is a thermos cup? What is a thermos cup? Are there any strict international requirements for thermos cups? As the name suggests, a vacuum flask is a water cup that preserves the temperature. This temperature represents both heat and cold, which means that the hot water in the water cup can be kept hot for a long time, and the cold water in the water cup can be kept cold for a long time. Internationally, there are definitions and regulations for thermos cups. Pour hot water at 96 degrees Celsius into the cup, seal the lid and let the water cup stand. After 6-8 hours, open the lid and test the water temperature at 55 degrees Celsius. It is a qualified thermos cup. Of course, this regulation was proposed many years ago. With the continuous improvement of production technology and craftsmanship, some thermos cups can even be kept warm for 48 hours through changes in product structure and craftsmanship.